Please don't misuse the code tags.

Use <p> tags in front of your text paragraphs, and keep the code tags for the real code sections. Thanks.

Your line 123 is reached and executed whether $gSDDdata[$sdd]{source} and/or $gSRSData[$srs]{sect} are defined or not.

Is that really what you want?

Maybe you want to take some action where you print your "m" and "n" (e.g. continue with the next loop)?

update: example added:

#!/usr/bin/perl
use strict;
use warnings;

my @out = ( 1, undef, 3 );
my @in  = ( 4, 5, undef );

OUTER: 
for my $o ( @out ) {
  INNER: 
  for my $i ( @in ) {
    if ( !defined $o ) {
      next OUTER;
    }
    
    if ( !defined $i ) {
      next INNER;
    }

    printf "\$o(%d) * \$i(%d) = %d\n", $o, $i, $o * $i;
  }
}
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