Not trying to go off topic, but isnt that code slightly redundant? after the first loop the output will always be the same. But back to the question. I do not get any errors using strict or warnings, or in the debugger. 
#!/usr/bin/perl -w

use strict;
use warnings;

my $x = 3;
my $y = 0;

for(1..3){
    $y = $x;     print "line 1 ---- x = $x -- y = $y\n";
    $y++;        print "line 2 ---- x = $x -- y = $y\n";
    $x -= $y;    print "line 3 ---- x = $x -- y = $y\n";
}

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EDIT: Updated code

In reply to Re: Debugger actions: On which lines? by james28909
in thread Debugger actions: On which lines? by worik

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