>perl -wMstrict -le
"my @lines = qw(abc 345  a1 1a a1a 1a1 abc1 1abc  a1==a1 a==1);
 printf '@lines: ';  printf qq{'$_' } for @lines;
 print qq{\n};
 ;;
 printf 'and 1: ';
 printf qq{'$_' } for grep { /[[:alpha:]]/ && /\d/ } @lines;
 print '';
 ;;
 printf 'regex 1: ';
 printf qq{'$_' } for grep m{ [[:alpha:]] \d | \d [[:alpha:]] }xms, @lines;
 print qq{\n};
 ;;
 ;;
 printf 'and 2:   ';
 printf qq{'$_' } for grep { !/[^[:alnum:]]/ && /[[:alpha:]]/ && /\d/ } @lines;
 print '';
 ;;
 my $al_num = qr{ [[:alpha:]] \d | \d [[:alpha:]] }xms;
 printf 'regex 2: ';
 printf qq{'$_' } for grep m{ \A [[:alnum:]]* $al_num [[:alnum:]]* \z }xms, @lines;
 print qq{\n};
 ;;
 ;;
 printf '@lines as was: ';
 printf qq{'$_' } for @lines;
"
@lines: 'abc' '345' 'a1' '1a' 'a1a' '1a1' 'abc1' '1abc' 'a1==a1' 'a==1'

and 1: 'a1' '1a' 'a1a' '1a1' 'abc1' '1abc' 'a1==a1' 'a==1'
regex 1: 'a1' '1a' 'a1a' '1a1' 'abc1' '1abc' 'a1==a1'

and 2:   'a1' '1a' 'a1a' '1a1' 'abc1' '1abc'
regex 2: 'a1' '1a' 'a1a' '1a1' 'abc1' '1abc'

@lines as was: 'abc' '345' 'a1' '1a' 'a1a' '1a1' 'abc1' '1abc' 'a1==a1' 'a==1'