The suggested File::Which is probably *the* solution you want.

The suggested File::Spec is probably (very) good to get used to when writing code that should work on all types of OS's.

I want to add that returning the actual path of the tool/program/script/file is a lot more useful than returning 1.

I also want to say that your approach is less than perfect as you do not skip empty $PATH elements and elements that do not exist or are not a directory. This matters a lot if you are dealing with environments where the environment cannot be trusted. I'd suggest (ignoring both mentioned modules):

use List::Util qw( first );

sub available {
    my $prog = shift;
    first { -x "$_/$prog } grep { m/\S/ && -d } split m/:+/ => $ENV{PA
+TH};
    }
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