You can match the end of the string witz \z, so if you have want to check if a string ends with bar, use m/bar\z/.

If you want to exclude a string from your search, you can use the negative lookahead: m/^(?!.*foo).*bar/ matches a string that contains a bar but no foo.

You can put it all together: to match a string that begins with foo, ends with bar and doesn't contain baz you can use this regex: m/\Afoo(?!.*baz).*bar\z/s

Most of the time it's easier to put all that into different regexes:

if (m/^foo/ && m/bar$/ && !m/baz/){
   ...
}
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See perlre for details

Given that they are constant strings that you are checking then your performance will be better splitting the test into three parts, substr to check for the start and end strings and index to check for the absence of the middle string. This is some benchmarking I did.

#!/net/perl/5.10.0/bin/perl
use strict;
use warnings;

use Benchmark qw(cmpthese);

my $str1 = join '', 'a' .. 'z';
my $str2 = join '', 'a' .. 'l', 'baz', 'm' .. 'z';
my $str3 = join '', 'a' .. 'z', 'a';

my $rx = qr/\Aabc(?!.*baz).*xyz\z/ms;

cmpthese(
    -1,
    {
        regex_match => sub { $str1 =~ /$rx/ },
        index_match => sub {
            substr( $str1, 0, 3 ) eq 'abc'
              && substr( $str1, -3 ) eq 'xyz'
              && index( $str1, 'baz' ) == -1;
        },
    }
);

cmpthese(
    -1,
    {
        regex_fail1 => sub { $str2 =~ /$rx/ },
        index_fail1 => sub {
            substr( $str2, 0, 3 ) eq 'abc'
              && substr( $str2, -3 ) eq 'xyz'
              && index( $str2, 'baz' ) == -1;
        },
    }
);

cmpthese(
    -1,
    {
        regex_fail2 => sub { $str3 =~ /$rx/ },
        index_fail2 => sub {
            substr( $str3, 0, 3 ) eq 'abc'
              && substr( $str3, -3 ) eq 'xyz'
              && index( $str3, 'baz' ) == -1;
        },
    }
);

__END__
                 Rate regex_match index_match
regex_match  337317/s          --        -73%
index_match 1228799/s        264%          --
                 Rate regex_fail1 index_fail1
regex_fail1  362337/s          --        -70%
index_fail1 1226609/s        239%          --
                 Rate regex_fail2 index_fail2
regex_fail2  865569/s          --        -48%
index_fail2 1653160/s         91%          --
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