Welcome to the monastery, Dervish!

As suggested, you should give a minimal piece of code that will compile and run and produce the issue you're having. In case you're not aware (though you've likely guessed), the message you're seeing is a non-fatal warning, which means you're invoking the script with -w or putting use warnings; at the top. This is usually (always?) a good thing to do.

What this particular warning is telling you is that you're attempting to use a regular expression against an undefined variable. Something like the following, for example, would produce a similar warning to what you're seeing. 
use warnings;## good line to have.  use strict; is also prudent
$x=undef;    ## I explicitly set it to undef here]
             ## even if I commented this, though, I'd have
             ## the same warning

($s)=$x=~m/regex/; ## $x is undefined, and produces warning
print $s;          ## presumably, I wanted $s for something

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You should definitely look at the line number suggested by the warning.

In reply to Re: Why? uninitialized value in pattern match when using if (defined) by SamCG
in thread Why? uninitialized value in pattern match when using if (defined) by Dervish

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