About half the PCs are XP/x86, and the other half are Windows 7/x64

Put a 32-bit perl on a network share. Give anyone wanting perl access to that share and set their assoc .pl to point to that shared perl. 32-bit Perls run perfectly on 64-bit Windows.

If there are some scripts that need/benefit from using a 64-bit perl, install a 64-bit perl on teh same share (different) path and set up associations for that using a different file extension (say .p64).

• When a user runs a script that needs 64-bit, they'll type theScript ...;
• that will resolve (via PATHEXT=.p64;.COM;.EXE;.BAT;.CMD;) to a file called theScript.p64;

  If it becomes necessary to have both 32-bit & 64-bit versions of a given script; then the 32-bit is call theScript.pl and because the machines with 32-bit OSs have their pathext set as PATHEXT=.pl;.COM;.EXE;.BAT;.CMD;; when they type theScript ..., it gets resolved to the 32-bit version.

• the association for that will be assoc .p64=Perl64
• the ftype for that will be ftype Perl64="P:\\perl64\bin\perl.exe" "%1" %*;

A similar set of associations for files named .pl run the 32-bit perl.

You have 2 centrally maintained, universally accessible builds of perl that everyone can use.

Getting them to use them is then a matter of political will and company process.