use strict;

my @keywords = qw/foo bar 12345 abcd/;
my $string = "foobarfoo1234523423412345abcdefsadfabc";

my $re = join('|',@keywords);

my %result;
$result{$1}++ while ($string =~ /($re)/ig);

foreach my $s (keys %result){
  print "$s=>$result{$s}\n";
}