Just for completeness and fun a simple GUI solution for the Mac using AppleScript:

set theWindowTitle to "PerlMonks"
set theSuffix to text returned of (display dialog "Enter a file suffix
+:" & return default answer "" with title theWindowTitle)
set theFolder to (choose folder with prompt "Enter directory")
set thePerlScript to quoted form of (POSIX path of ((choose file with 
+prompt "Select a script:") as Unicode text))

-- display dialog "Script: " & thePerlScript with title theWindowTitle

tell application "Finder"
    set theFiles to (every file of theFolder whose name extension is t
+heSuffix) --as alias list
end tell

repeat with theFile in theFiles
    set theFile to quoted form of (POSIX path of (theFile as Unicode t
+ext))
    display dialog "Found: " & theFile with title theWindowTitle
    set theResult to do shell script thePerlScript & " " & theFile
    display dialog "Result: " & theResult with title theWindowTitle
    -- beep
end repeat


[download]

Perl script:

#!/usr/bin/perl

while (<>) {print}
[download]

Files:

Karls-Mac-mini:find karl$ cat foo.txt bar.txt 
foo
bar

[download]

Regards, Karl