use utf8::all;

my $str = <<'EOF';
global.lifeTime=\u00C9lettartam
global.lifeTime_from=\u00C9lettartam \u00F3ta
global.lifeTime_to=\u00C9lettartam eddig
fastExport.tooltip=Javaslat a lapoz\u00E1sra\: kattintson a grafik\u00E1ra <br /> Tartsa lenyomva a bal eg\u00E9rgombot, mik\u00F6zben az egeret mozgatja.
EOF

$str =~ s{ \\u([0-9A-F]{4}) }{ chr hex $1 }egix;

print $str;