You can use Regular Expressions to search Gmail with the help of Google App Script. The script scans the mailbox, compares the message body with the search pattern and prints any matching messages. Google Apps Script using standard JavaScript functions to perform regex search.

function Search() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var row = 2;

  // Clear existing search results
  sheet.getRange(2, 1, sheet.getMaxRows() - 1, 4).clearContent();

  // Which Gmail Label should be searched?
  var label = sheet.getRange('F3').getValue();

  // Get the Regular Expression Search Pattern
  var pattern = sheet.getRange('F4').getValue();

  // Retrieve all threads of the specified label
  var threads = GmailApp.search('in:' + label);

  for (var i = 0; i < threads.length; i++) {
    var messages = threads[i].getMessages();

    for (var m = 0; m < messages.length; m++) {
      var msg = messages[m].getBody();

      // Does the message content match the search pattern?
      if (msg.search(pattern) !== -1) {
        // Format and print the date of the matching message
        sheet.getRange(row, 1).setValue(Utilities.formatDate(messages[m].getDate(), 'GMT', 'yyyy-MM-dd'));

        // Print the sender's name and email address
        sheet.getRange(row, 2).setValue(messages[m].getFrom());

        // Print the message subject
        sheet.getRange(row, 3).setValue(messages[m].getSubject());

        // Print the unique URL of the Gmail message
        var id = 'https://mail.google.com/mail/u/0/#all/' + messages[m].getId();
        sheet.getRange(row, 4).setFormula('=hyperlink("' + id + '", "View")');

        // Move to the next row
        row++;
      }
    }
  }
}