my ( $week, $comptage, $index ) = qw{ W C I };
my $cmdc2= qq{mv M3.*txt ../../../dir_first_action_${week}/dir_M3_${week}_comptage_${comptage}_${index}};
print $cmdc2;
#Output:
#mv M3.*txt ../../../dir_first_action_W/dir_M3_W_comptage_C_I