Using it the way you describe will cause porting issues for older perl versions:

$ perl -MFile::Glob::bsd_glob -wE'say for bsd_glob ("*.foo")'
Can't locate File/Glob/bsd_glob.pm in @INC (@INC contains: /pro/lib/pe
+rl5/site_perl/5.14.2/IA64.ARCHREV_0-LP64-ld /pro/lib/perl5/site_perl/
+5.14.2 /pro/lib/perl5/5.14.2/IA64.ARCHREV_0-LP64-ld /pro/lib/perl5/5.
+14.2 .).
BEGIN failed--compilation aborted.
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edit: correct above example of failure. The correct syntax is just as bad though:

$ perl -MFile::Glob=:bsd_glob -wE'say for bsd_glob ("*.foo")'
"bsd_glob" is not defined in %File::Glob::EXPORT_TAGS at /pro/lib/perl
+5/5.14.2/IA64.ARCHREV_0-LP64-ld/File/Glob.pm line 45.
        File::Glob::import("File::Glob", ":bsd_glob") called at -e lin
+e 0
        main::BEGIN() called at -e line 0
        eval {...} called at -e line 0
Can't continue after import errors at -e line 0.
BEGIN failed--compilation aborted.
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And additional shit hits the fan when you would try to install it

$ cpan File::Glob
:
The most recent version "1.28" of the module "File::Glob"
is part of the perl-5.26.1 distribution. ...
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Does this in your opinion imply that File::Glob should be dual-lived?

The current (today) absolute advised minimum version to be supported by the toolchain is perl-5.8.1. My example with 5.14.2 could arguably be considered recent enough.

Digging in the Delta's:

perl561delta.pod:
  File::Glob::glob() has been renamed to File::Glob::bsd_glob()

perl58delta.pod:
  File::Glob::glob() has been renamed to File::Glob::bsd_glob()

perl5160delta.pod:
  It has a new C<:bsd_glob> export tag, intended to replace C<:glob>.

perl5260delta.pod:
  L<C<File::Glob::glob()> will disappear in perl 5.30. Use C<File::Glo
+b::bsd_glob()> instead.
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Does *not* make me happy. I see the trouble that is addressed, but this makes portable programming much much harder. Looks like the only portable way to write it from 5.6.1 to blead is:

use File::Glob;

my @files = File::Glob::bsd_glob ("*.txt");
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Safe, but not really a nice replacement of the simple <*.txt> or glob ("*.txt").