Perl: Adding an exception to a foreach loop - loops

Question

I'm new to Stack Overflow and I would like to ask for some advice with regard to a minor problem I have with my Perl code.
In short, I have written a small programme that opens text files from a pre-defined array, then searches for certain strings in them and finally prints out the line containing the string.
my #S1A_SING_Files = (
'S1A-001_SING_annotated.txt',
'S1A-002_SING_annotated.txt',
'S1A-003_SING_annotated.txt',
'S1A-004_SING_annotated.txt',
'S1A-005_SING_annotated.txt'
);
foreach (#S1A_SING_Files) {
print ("\n");
print ("Search results for $_:\n\n");
open (F, $_) or die("Can't open file!\n");
while ($line = <F>) {
if ($line =~ /\$(voc)?[R|L]D|\$Rep|\/\//) {
print ($line);
}
}
}
close (F);
I was wondering whether it is possible to create an exception to the foreach loop, so that the line containing
print ("\n");
not be executed if the file is $S1A_SING_Files[0]. It should then be normally executed if the file is any of the following ones. Do you think this could be accomplished?
Thank you very much in advance!

Answer 1

Yes. Just add a check for the first file. Change:
print ("\n");
to:
print ("\n") if $_ ne $S1A_SING_Files[0];

Answer 2

If the array contains unique strings, you can use the following:
print("\n") if $_ ne $S1A_SING_Files[0]; # Different stringification than 1st element?
The following will work even if the array contains non-strings or duplicate values (and it's faster too):
print("\n") if \$_ != \$S1A_SING_Files[0]; # Different scalar than 1st element?
Both of the above could fail for magical arrays. The most reliable solution is to iterate over the indexes.
for my $i (0..$#S1A_SING_Files) {
my $file = $S1A_SING_Files[$i];
print("\n") if $i; # Different index than 1st element?
...
}

Answer 3

Your code can be written in following form
use strict;
use warnings;
my #S1A_SING_Files = (
'S1A-001_SING_annotated.txt',
'S1A-002_SING_annotated.txt',
'S1A-003_SING_annotated.txt',
'S1A-004_SING_annotated.txt',
'S1A-005_SING_annotated.txt'
);
foreach (#S1A_SING_Files) {
print "\n" unless $_ ne $S1A_SING_Files[0];
print "Search results for $_:\n\n";
open my $fh, '<', $_ or die("Can't open file!\n");
m!\$(voc)?[R|L]D|\$Rep|//! && print while <$fh>;
close $fh;
}