How to randomly pair items in a list - perl

Question

I have a list of Accession numbers that I want to pair randomly using a Perl script below:
#!/usr/bin/perl -w
use List::Util qw(shuffle);
my $file = 'randomseq_acc.txt';
my #identifiers = map { (split /\n/)[1] } <$file>;
chomp #identifiers;
#Shuffle them and put in a hash
#identifiers = shuffle #identifiers;
my %pairs = (#identifiers);
#print the pairs
for (keys %pairs) {
print "$_ and $pairs{$_} are partners\n";
but keep getting errors.
The accession numbers in the file randomseq_acc.txt are:
1094711
1586007
2XFX_C
Q27031.2
P22497.2
Q9TVU5.1
Q4N4N8.1
P28547.2
P15711.1
AAC46910.1
AAA98602.1
AAA98601.1
AAA98600.1
EAN33235.2
EAN34465.1
EAN34464.1
EAN34463.1
EAN34462.1
EAN34461.1
EAN34460.1

Answer 1

I needed to add the closing right curly brace to be able to compile the script.
As arrays are indexed from 0, (split /\n/)[1] returns the second field, i.e. what follows newline on each line (i.e. nothing). Change it to [0] to make it work:
my #identifiers = map { (split /\n/)[0] } <$file>; # Still wrong.
The diamond operator needs a file handle, not a file name. Use open to associate the two:
open my $FH, '<', $file or die $!;
my #identifiers = map { (split /\n/)[0] } <$FH>;
Using split to remove a newline is not common. I'd probably use something else:
map { /(.*)/ } <$FH>
# or
map { chomp; $_ } <$FH>
# or, thanks to ikegami
chomp(my #identifiers = <$FH>);
So, the final result would be something like the following:
#!/usr/bin/perl
use warnings;
use strict;
use List::Util qw(shuffle);
my $filename = '...';
open my $FH, '<', $filename or die $!;
chomp(my #identifiers = <$FH>);
my %pairs = shuffle(#identifiers);
print "$_ and $pairs{$_} are partners\n" for keys %pairs;