PERL Beginners - simple substitution question

Author

simple substitution question

Harold Castro

2005-02-18, 3:56 am

Hi,
There is something that's bothering me for so long
regarding the use of $_ variable.

for example:
here is my string:
$_ = "but";
s/u/a/g;
print $_;

This will simply print "bat"

My problem is using a variable in place of $_.
how will I tell that the one i'm going to substitute
is the $string;
Ex:
my $string = "but";
s/u/a/g;
print $string;

and I get this error when i run it.

Use of uninitialized value in substitution (s///) at
substitute line 6.

I don't have any trouble with regex matching using $_
or any varible because I can always say:
if $variable =~/\d/ instead of:
if(/\d/) which is equivalent to $_=~/\d/;

I don't know how to do it with substitutions.

any idea?
thanks

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Bedanta Bordoloi

2005-02-18, 8:56 am

Hi,

If I've understood your problem, what you can simply try is

$string = "but";
print "Before: $string ";
$string =~ s/u/a/g;
print "After: $string\n";

You will get as output

$ Before: but After: bat

Cheers,
Bedanta

-----Original Message-----
From: Harold Castro [mailto:b0ydaem0n@yahoo.com]
Sent: Friday, February 18, 2005 12:17 PM
To: beginners@perl.org
Subject: simple substitution question

Hi,
There is something that's bothering me for so long
regarding the use of $_ variable.

for example:
here is my string:
$_ = "but";
s/u/a/g;
print $_;

This will simply print "bat"

My problem is using a variable in place of $_.
how will I tell that the one i'm going to substitute
is the $string;
Ex:
my $string = "but";
s/u/a/g;
print $string;

and I get this error when i run it.

Use of uninitialized value in substitution (s///) at
substitute line 6.

I don't have any trouble with regex matching using $_
or any varible because I can always say:
if $variable =~/\d/ instead of:
if(/\d/) which is equivalent to $_=~/\d/;

I don't know how to do it with substitutions.

any idea?
thanks

__________________________________
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Ing. Branislav Gerzo

2005-02-18, 8:56 am

Harold Castro [HC], on Thursday, February 17, 2005 at 22:47 (-0800
(PST)) typed:

HC> for example:
HC> here is my string:
HC> $_ = "but";
HC> s/u/a/g;
HC> print $_;

what about this:
( my $string = "but" ) =~ s/u/a/g;

--

...m8s, cu l8r, Brano.

[Old Farts don't have to be politically correct.]

Manav Mathur

2005-02-18, 8:56 am

=~ is the bind operator.
see perldoc perlop.

Manav

-----Original Message-----
From: Harold Castro [mailto:b0ydaem0n@yahoo.com]
Sent: Friday, February 18, 2005 12:17 PM
To: beginners@perl.org
Subject: simple substitution question

Hi,
There is something that's bothering me for so long
regarding the use of $_ variable.

for example:
here is my string:
$_ = "but";
s/u/a/g;
print $_;

This will simply print "bat"

My problem is using a variable in place of $_.
how will I tell that the one i'm going to substitute
is the $string;
Ex:
my $string = "but";
s/u/a/g;
print $string;

and I get this error when i run it.

Use of uninitialized value in substitution (s///) at
substitute line 6.

I don't have any trouble with regex matching using $_
or any varible because I can always say:
if $variable =~/\d/ instead of:
if(/\d/) which is equivalent to $_=~/\d/;

I don't know how to do it with substitutions.

any idea?
thanks

__________________________________
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Read only the mail you want - Yahoo! Mail SpamGuard.
http://promotions.yahoo.com/new_mail

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To unsubscribe, e-mail: beginners-unsubscribe@perl.org
For additional commands, e-mail: beginners-help@perl.org
<http://learn.perl.org/> <http://learn.perl.org/first-response>

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