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use Time::Piece; localtime()->strptime(@ARGV[0], "%Y-%m");
bash$ perl -e 'use Time::Piece; localtime()->strptime(@ARGV[0], "%Y +-%m"); print "ok\n"; ' "2019-01" ... Error parsing time at /usr/lib/x86_64-linux-gnu/perl/5.26/Time/Piece.p +m line 481.