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in reply to Frustrating Error: "Global symbol requires explicit package name" - Can't see why?

When you get a cryptic syntax error which you can't understand how you got, run through Basic debugging checklist, especially perl -MO=Deparse:
$ perl -MO=Deparse #!/usr/bin/perl use strict; use warnings; use threads; my $t1 = async { qx(perl process1); } my $t2 = async { qx(perl process2); } my @out1 = $t1->join; __END__ Global symbol "$t1" requires explicit package name at - line 10. - had compilation errors. use threads; use warnings; use strict; my $t1 = async(sub { `perl process1`; } , my $t2 = async(sub { `perl process2`; } , my(@out1) = ${'t1'}->join));
As Deparse clearly shows, absence of semicolons chained the calls to async and join together, making them arguments to each other.