use strict;

my @lines0;  # using your array name

# ...do whatever you do to fill @lines0...

my $totalsec = 0;

for ( @lines0 ) {
    my @words = split /\s+/;
    my ( $hrs, $mins, $secs ) = split /:/, pop @words;
    $totalsec += ( $hrs * 60 + $mins ) * 60 + $secs;
}

printf( "Total time is %d minutes and %d seconds\n",
        int( $totalsec / 60 ), $totalsec % 60 );