The problem is perl's parser/interpretter which doesn't properly record the line number of the various bits of an if. Consider:

#! /usr/bin/perl

my $a = "foo";
if ( $a =~ m/aa/ ) {
  print "hello";
 } elsif ( nonexistant() ) {
  print "hello";
 } else { }
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Which says

Undefined subroutine &main::nonexistant called at - line 4.
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Basically everything in the conditions of an if statement appears to be on the same line as the if.

It sucks but it's a known issue and not likely to be fixed any time soon. If I recall correctly, the way perl currently works, to fix this would mean that each block in the if would require it's own stack frame, which is too much overhead.