my @values = qw(
 rtxecx38006_1439
 wtxecx380d1_1927
 wtxecx38009_0028
 ccaecx34000_4430
 lcaecx38000_1453
 kmohuspvmwo@171.197.27.110
 rtxecx38005_2604
 wtxecx380d0_0057
);

s/[_@].*//, print "$_\n" for @values;
[download]

I think (and hope) choroba has hit your definition of "special characters" on the head.... even if it is a specification that is utterly non-standard, arcane, and imprecise.

You should have provided that specification because "special characters" has special meanings in certain contexts -- and because the solution offered keeps some numbers and deletes others... in conformity with your example. But defining a spec based on a small example/sample is a risky and often ambiguous process.

I dislike using regexes when simple string functions can handle the job.

By extracting the magic delimiter characters into a predefined constant, the code is clearer and more easily extendable. split will partition an input string on any of those special characters, and the wrapper (xx)[0] extracts the first element from the resulting list.

my @DELIMS = (qw( _ @ ));

for my $elem ( @inputs ) {
    push @result, ( split /[@DELIM]/, $elem )[0];
}
 
[download]

... I dislike using regexes..
But your usage of "split" ... split /[@DELIM]/, $elem .. is still regexes...
Or you say otherwise?

my @DELIMS = (qw( _ @ ));
...
... /[@DELIM]/ ...
[download]

If the default value of  $" is unchanged, the array  @DELIMS will be interpolated into the regex character class with an extraneous space character, which is then a valid part of the class: a bug waiting to happen. Locally set  $" to the empty string or, better yet, use join to form the char class string.

>perl -wMstrict -le
"my @DELIMS = (qw( _ @ ));
 ;;
 my $rx = qr{[@DELIMS]};
 print $rx;
 ;;
 { local $\" = '';  $rx = qr{[@DELIMS]}; }
 print $rx;
 ;;
 my $cc = join '', @DELIMS;
 $rx = qr{[$cc]};
 print $rx;
"
(?^:[_ @])
(?^:[_@])
(?^:[_@])
[download]

Do not multiply bugs without necessity!