&POSIX::strftime has all you want:

use POSIX qw( strftime );
print strftime( '%Y-%m-%d %T', localtime);
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See 'man 2 strftime' for all the format codes available. POSIX man page tells about portability and perlish concerns.

Update: Shortened the format with %T; was %H:%M:%S.

After Compline,
Zaxo