G'day samh785,

The special variables $1, $2, etc. are reinitialized on each match. This includes matches done as part of a substitution. After '$mac1 =~ s/:/-/g;', which contains no captures, both $1 and $2 are uninitialized.

Here's a example: 

#!/usr/bin/env perl -l

use strict;
use warnings;

my $string = 'abc|def';

if ($string =~ /(\S{3})\|(\S{3})/) {
    print "After first match (in if condition): \$1=$1 \$2=$2";
    my $whatever = 'blah';
    $whatever =~ s/b/c/;
    print "After second match (in substitution): \$1=$1 \$2=$2";
}

[download]

Output:

After first match (in if condition): $1=abc $2=def
Use of uninitialized value $1 in concatenation (.) or string at ./pm_1
+143443_match_vars.pl line 12.
Use of uninitialized value $2 in concatenation (.) or string at ./pm_1
+143443_match_vars.pl line 12.
After second match (in substitution): $1= $2=

[download]

Assigning $2 to $mac2 before attempting the substitution should fix your problem.

— Ken

In reply to Re: Can anyone tell me what is going on with my code?(Regex match variables) by kcott
in thread Can anyone tell me what is going on with my code?(Regex match variables) by samh785

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