Take a two-step approach: First isolate the core part of the string between "foo" and "bar". Use a global match to extract all numeric sequences from the core in one more step. 
while ( <DATA> ) {
    my ( $core) = /^foo (.*) bar$/;
    my @nums = $core =~ /m (\d+)/g;
    print "$core -> (@nums)\n";
}

__DATA__
foo m 1 m 2 m 3 m 4 bar
foo m 2 m 4 m 7 bar
foo m 1 bar

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That assumes there is only one delimiting pair of "foo" ... "bar"per string.

Anno

In reply to Re: Arbitrary number of captures in a regular expression by Anno
in thread Arbitrary number of captures in a regular expression by grinder

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