C:\Users\Corion>perl -le "warn 'foo';print 'bar'"
foo at -e line 1.
bar

C:\Users\Corion>perl -le "warn 'foo';print 'bar'" >tmp.txt
foo at -e line 1.

C:\Users\Corion>perl -le "warn 'foo';print 'bar'" 2>&1 >tmp.txt
foo at -e line 1.

C:\Users\Corion>ver

Microsoft Windows [Version 6.1.7601]

C:\Users\Corion>