$ perl -wle "open(FOO, '-|') || exec 'perl someprog';  print <FOO>"
%DCL-W-IVVERB, unrecognized command verb - check validity and spelling \$\
%DCL-W-IVVERB, unrecognized command verb - check validity and spelling \$\

but the very new three arg version does.

$ perl -wle "open(FOO, '-|', 'perl bug');  print <FOO>"
2

I suspect it's a PerlIO thing.

$ perl -v

This is perl, v5.7.2 built for VMS_AXP