perl - Why I can't pass one argument to sub -

input directory name , output text file name in directory , file's name, line count, word count. when checked program, know when second sub working, $_ nothing "".

how should fix ?

#!/usr/bin/perl use strict; use warnings; $dir = <stdin>; chomp($dir); # remove '\n'(new-line character) directory address opendir(dirhandle, "$dir");  @arr = readdir(dirhandle); close(dirhandle); foreach(@arr){     if($_ =~ /.txt/){         print "file name : $_\n";                $tmp = $_;         print "line numb : ".&how_many_lines($_)."\n";         print "word numb : ".&how_many_words($_)."\n\n";     } } sub how_many_lines{     open(file, "$_") || die "can't open '$_': $!";     $cnt=0;     while(<file>){          $cnt++;     }     close(file);     return $cnt; } sub how_many_words{     open(text, "$_") || die "can't open '$_': $!";     # error! printed "can't open ''" : no such file or directory     $cnt=0;     while(<text>){         @tmp = split(/ /, $_);         $num = @tmp;         $cnt += $num;     }     close(text);     return $cnt; } 

you cannot refer first argument of sub $_. should $_[0], first element of array @_, list of arguments.

the idiomatic (not confused idiotic) way of retrieving arguments in sub this:

my $filename = shift;  # shift uses @_ automatically without arguments 

perl allows same names scalars, arrays , hashes: $foo, @foo, %foo different entities. when index array @foo zero, becomes $foo[0]. not same $foo.