undefined subroutine &main::Copy

File::Copy exports a sub named copy, not Copy.

$ perl -le'use File::Copy qw( Copy ); print "ok"'
"Copy" is not exported by the File::Copy module
Can't continue after import errors at -e line 1
BEGIN failed--compilation aborted at -e line 1.

$ perl -le'use File::Copy qw( copy ); print "ok"'
ok
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global symbol $_ requires explicit package name

Well, you won't get that error for $_ specifically — it's special — but it's correctly claiming that you didn't declare any of your other variables.

...
my $dirpath=...
...
while (defined (my $file = ...) ) {
...
foreach my $filename (...) {
...
}
...
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