FTYPE [fileType[=[openCommandString]]]

fileType

Specifies the file type to examine or change

openCommandString

Specifies the open command to use when launching files of this type.

Type FTYPE without parameters to display the current file types that have open command strings defined. FTYPE is invoked with just a file type, it displays the current open command string for that file type. Specify nothing for the open command string and the FTYPE command will delete the open command string for the file type. Within an open command string %0 or %1 are substituted with the file name being launched through the assocation. %* gets all the parameters and %2 gets the 1st parameter, %3 the second, etc. %~n gets all the remaining parameters starting with the nth parameter, where n may be between 2 and 9, inclusive. For example:

ASSOC .pl=PerlScript
FTYPE PerlScript=perl.exe %1 %*

would allow you to invoke a Perl script as follows:

script.pl 1 2 3

If you want to eliminate the need to type the extensions, then do the
following:

set PATHEXT=.pl;%PATHEXT%

and the script could be invoked as follows:

script 1 2 3