Does the text file contain a blank line?
rocroc:
Here's an example of behavior when processing a blank line or a line having empty or too few fields: an empty or missing field splits to an empty string or to undef. The reason for the seemingly spurious match is that an empty string or an undef becomes the // regex, which always matches!
>perl -wMstrict -le
"my $s = 'foo,,';
;;
my ($field0, $field1, $field2, $field3) = split /,/, $s;
print qq{field0 '$field0' field1 '$field1' field3 '$field3'};
;;
if ('bar' =~ m{ $field1 }xms) { print qq{bar matches '$field1'} }
if ('bar' =~ m{ $field3 }xms) { print qq{bar matches '$field3'} }
"
Use of uninitialized value $field3 in concatenation (.) or string ...
field0 'foo' field1 '' field3 ''
bar matches ''
Use of uninitialized value $field3 in regexp compilation ...
Use of uninitialized value $field3 in concatenation (.) or string ...
bar matches ''
Note that without warnings (you are using warnings, aren't you?), this all proceeds quite silently:
>perl -Mstrict -le
"my $s = 'foo,,';
;;
my ($field0, $field1, $field2, $field3) = split /,/, $s;
print qq{field0 '$field0' field1 '$field1' field3 '$field3'};
;;
if ('bar' =~ m{ $field1 }xms) { print qq{bar matches '$field1'} }
if ('bar' =~ m{ $field3 }xms) { print qq{bar matches '$field3'} }
"
field0 'foo' field1 '' field3 ''
bar matches ''
bar matches ''
