sub fill_hash {
# get filename
print "Enter 'ls' or a filename to scan: ";
my $file_name = shift || ;
while ($file_name =~ m/^ls/) {
system("$file_name");
print "\nEnter 'ls' or a filename to scan: ";
$file_name = ;
}

##</code><code>##

syntax error at foo line xx, near "|| ;"

##</code><code>##

map{$s{$_}++}/./gfor<>