#!/usr/bin/perl -w
use strict;
use warnings;

my @GI = ("gi|Q384722390|emb|WP_938420210.1|Gene name",
    "gi|342546780|emb|WP_934203412.1|Gene name");
my @Accession = ("WP_938420210.1","WP_934203412.1");

# Convert to hash
my %foo = ();
for my $gene (@GI) {
    my @fields = split (/\|/, $gene);
    $foo{$fields[3]} = $gene;
}

# Now extract
for my $accno (@Accession) {
    print "Acc no: $accno, Gene: $foo{$accno}\n";
}