Then running argcount 'a b c' returns 1, but running ssh localhost argcount 'a b c' returns 3. Moreover, running ssh localhost argcount 'a;b;c' exhibits even more undesirable behavior.

This is more a shell question, than a Perl question. In fact, it's totally irrelevant in which language argcount is written.

But here are some things you want to try:

• ssh localhost argcount "'a b c'"
• ssh localhost "argcount 'a b c'"
• ssh localhost argcount \'a b c\'
• ssh localhost argcount a\\\ b\\\ c
• ssh localhost argcount "'"a b c"'"