Rather than comment on your code, let me first argue against building an SQL command by concatenating strings together -- it makes things really clumsy,

Instead, the approach that I follow is to write the final command that I'm going to submit to the prepare method ..

my $cmd = "INSERT INTO $table ($fields) VALUES ($placeholderList)";
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.. and then work backwards, filling bits in as I go. The sub preamble will be something like this ..

#  Accepts a database handle, a table name, and a hashref
#  of field names and values. Returns on success, otherwise
#  dies.

sub addData
{
  my ( $dbh, $table, $args ) = @_;
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Now it's time to build the pieces leading up to your command ..

  #  Get a comma separated list of the field names ..
  my $fields = join(',', keys %$args);

  #  Get the values into an array ..
  my @values = values %$args;

  #  Get a comma separated list of '?', one for each value
  #  ..
  my $placeholderList = join(',',('?') x @values);
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Then, once the command is built, you do the rest of the stuff with the database ..

  #  Prepare the command and execute it with the array of
  #  values.
  my $sth = $dbh->prepare($cmd);
  $sth->execute(@values) or die $sth->error;

  return 0;     # Success!
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So in the end you have a piece of code that's clean and fairly well documented. Once more, here's the entire thing:

#  Accepts a database handle, a table name, and a hashref
#  of field names and values. Returns on success, otherwise
#  dies.

sub addData
{
  my ( $dbh, $table, $args ) = @_;

  #  Get a comma separated list of the field names ..
  my $fields = join(',', keys %$args);

  #  Get the values into an array ..
  my @values = values %$args;

  #  Get a comma separated list of '?', one for each value ..
  my $placeholderList = join(',',('?') x @values);

  #  Build the entire command ..
  my $cmd = "INSERT INTO $table ($fields) VALUES ($placeholderList)";

  #  Prepare the command and execute it with the array of values.
  my $sth = $dbh->prepare($cmd);
  $sth->execute(@values) or die $sth->error;

  return 0;     # Success!
}
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Way cleaner, no?