regex - Perl: grep is matching when it should not -

sub process_ignore{     $col_ref = shift;     $ignore_ref = shift;     foreach ( @{$ignore_ref} ) {         if ( grep( /^$_$/, @{$col_ref})) {             print "will ignore column: $_\n" if $debug;              } else {             print "will not ignore column: $_\n because not valid column" if $debug;         }     }      if ($debug) {         foreach $val ( @{$col_ref} ) {             print "$val\n";         }     } }  &process_ignore(\@cols, \@ignores) 

--
@cols have a_id, status, stime
@ignores have a_id, sdd

output:
ignore column: a_id
ignore column: sdd
a_id status
stime

i m not sure why going the matching if block when should not.
there no sdd in @cols

also, grep ignore case? i.e a_id vs a_id?

replace:

foreach ( @{$ignore_ref} ) { if ( grep( /^$_$/, @{$col_ref})) {

to(at least):

foreach $ignore ( @{$ignore_ref} ) { if ( grep( /^$ignore$/, @{$col_ref})) {

or even(if regexp not necessary):

foreach $ignore ( @{$ignore_ref} ) { if ( grep {$_ eq $ignore} @{$col_ref} ) {