The 'perldoc' binary has to know where to look for your script (somewhat like the path to find modules). The filters (like pod2text and pod2html) can work on it by filename directly:

$ pod2text file.pl | less
[download]

Perldoc can work on installed modules:

perldoc HTML::Template
[download]

Or on specific perl documentation:

perldoc perlref
[download]

Or, using the -f switch, on a builtin function:

perldoc -f print
[download]