#!/bin/perl

# credentials / environment variables
$ORACLE_HOME="/u01/app/oracle/product/10.2.0.4";
$ORACLE_SID=qaecom1;
$sqlplus="/u01/app/oracle/product/10.2.0.4/bin/sqlplus";
$USERNAME=dbuser;
$PASS=pass;
$SID=${ORACLE_SID};

# Get all the data at once
@TSPACES=`$sqlplus -s -l $USERNAME/$PASS@$SID \@/opt/bin/ops/mlb_tablespace.sql`;

# Now split the 4 columns you want into separate arrays,
# and then join those arrays in the order you want:
{
  my (@col1, @col2, @col3, @col4);
  for (@TSPACES) {
      my @cols = split;
      push @col1, $cols[0];
      push @col2, $cols[1];
      push @col3, $cols[2];
      push @col4, $cols[3];
  }
  @TSPACES = (@col1, @col2, @col3, @col4);
}

# ... the rest of your script