# no redirection
C:\>perl -e "warn 'foo'"
foo at -e line 1.

# redirect STDERR to FILE (often /dev/null :-)
C:\>perl -e "warn 'foo'" 2> out
C:\>type out
foo at -e line 1.

# redirect STDERR to STDOUT
C:\>perl -e "warn 'foo'" 2>&1
foo at -e line 1.

# redirect STDERR to STDOUT and STDOUT to FILE
C:\>perl -e "warn 'foo';print 'bar'">out  2>&1
C:\>type out
foo at -e line 1.
bar