use strict;
use warnings;

my @DataA = split /\n/, <<DATAA;
A   "Monday"
B   "Tuesday"
C   "Wednesday"
D   "Thursday"
DATAA

my @DataB = split /\n/, <<DATAB;
M    252   212  "Bill"
A    325   908  "Jim"
C    426   907  "Mike"
A    423   383  "Sally"
A    993   421  "Jim"
C    737   432  "Mary"
DATAB

my %AHits;
my @merged;

for (@DataA) {
    my ($key, $day) = split /\s+/;
    
    $AHits{$key} = $day;
}

for (@DataB) {
    my ($key, @params) = split /\s+/;
    
    next unless exists $AHits{$key};
    
    push @merged, [$key, $AHits{$key}, @params];
}

print join ("\t", @$_), "\n" for sort {$a->[0] cmp $b->[0]} @merged;

##</code><code>##

A	"Monday"	325	908	"Jim"
A	"Monday"	423	383	"Sally"
A	"Monday"	993	421	"Jim"
C	"Wednesday"	426	907	"Mike"
C	"Wednesday"	737	432	"Mary"