#does your system support shebang (#!)?
$perl = $^X =~ m%/% ? $^X: eval {
    use Config;
    return $Config{"installbin"}."/perl"; };
print "Is this perl [$perl]? (n,Y)\n";
$answer = <>;
if( $answer !~ /y/i && $answer !~ /^$/ ){
    print "Shell thinks perl is here: ", `which perl`;
    print "Please enter the location of perl now:\n";
    $perl = <>;
}
print "Replacing #!/usr/bin/perl with #!$perl\n";